GB2191599A - Apparatus for measuring distances and angles - Google Patents

Abstract

The apparatus comprises means for projecting first and second beams of light, an arrangement for inclining one beam relatively to the other, means for measuring the inclination and further means for imparting angular movement to one of the beams about an axis lying in the plane containing the beams and for measuring the movement. One embodiment comprises a housing (2) accommodating a laser (1). Positioned in the path of the laser beam (3) is a beam splitting mirror (4) which divides the beam along two separate parts (5, 6). One part (5) emerges from the housing via an aperture (7) while the other part (6) is reflected by a reflector (8) through a slot (9) in the housing. Reflector (8) is mounted for pivotal movement. Distances are measured by directing part (5) towards an object and then rotating reflector (8) until coincidence on the object is obtained. Part (2a) of the housing is rotatable to allow angular movement of the one beam (5). <IMAGE>

Description

SPECIFICATION Improvements in or relating to apparatus for measuring distances and angles This invention relates to apparatus for measuring distances and angles.

G.B. Patent Application No. 86.05508 describes apparatus that uses laser beams to measure the distance of an object from a reference point and it is an object of the present invention to provide a modified form of that apparatus that can be used to measure angles as well as distances.

According to the present invention, apparatus for measuring distances and angles comprises means for projecting a beam of light from the apparatus, an arrangement for projecting from the apparatus a second beam of light that is spaced from the first beam, an arrangement for inclining one beam relativelyto the other, means for measuring the inclination, further means for rotating one of the beams about an axis lying in the plane and containing the first and second beams and for measuring that rotation.

In a preferred embodiment of the invention, one only ofthe beams can be inclined and only the other beam is rotatable.

The light beams may be beams of coherent light provided by one or more lasersources.

The or each laser source may be a continuous wave laser or it may be pulsed at a frequency high enough to create the visual impression of con tinuouswave operation.

The or each laser source may be a ruby laser or a gas laser, for example a helium-neon laser or a helium cadmium laser.

The inclination ofthe one beam may be effected by a pivotally mounted reflector.

The rotation of the other beam may be effected by rotating a part of the apparatus or by means of a rotatable refractor.

By way of example only, an embodiment of the invention will now be described with reference to the accompanying drawings of which: Figure lisa schematic layout ofthe embodiment illustrating its method of operation, and Figure 2 is a perspective view of a hand-held embodiment of the invention.

Basically, the invention provides means for pro- jecting a first beam of light towards an object, an arrangementfor projecting a second beam of light towards the object, the second beam being spaced fromthefirst beam, and means for inclining one of the beams relatively to the other and for measuring the degree of inclination, and an arrangement for rotating one of the beams about an axis lying in the plane containing the first and second beams and for measuring the degree of rotation.

Figure 1 shows schematicaliy a particular arrangement using a single laser source indicated by block 1 that is located in a housing 2. Also located within the housing 2 and positioned in the path of the beam 3 of coherent lightfrom laser lisa beam splitting mirror 4. The mirror4 divides the beam 3 in equal parts 5,6 of which part 5 passes out of the housing through an aperture7 in a wall thereof.

Part6 is directed by mirror4towards a reflector8 positioned to direct the partthrough a slot 9 in the wall of the housing 2.

Reflector 8 is mounted for pivotal movement about an axis 10 that is normal to the plane containing the parts 5 and 6 and that is usually horizontal. Means are provided for varying the inclination of the reflector and aboutthe axis 10 and for indicating very ac curatelytheextentofthe inclination.

Mounted externallyofthe housing 2 is a control, operation of which by a user rotates the reflector 8 about its pivotal axis 10. The control may be a knob directly mounted upon a shaft lying along the pivotal axis 10 or it may comprise a slow motion driveforthe shaftthatenablesthe userto rotate the shaft very accurately.

Rotation indicating means shown diagrammatically at 11 may include a vernier type scale that en- ablesthe rotational movement of the reflector8to be measured to a required degree of accuracy depending upon the range of distance for which the apparatus is designed. For example, for distances up to several hundreds of feet (or say 100 metres) measurementto 1 ' of arc is needed.

Preferably, however, reflector 8 is fitted with a shaftencoderthatelectronicallyscansa scalemovable with the reflector. The output of the encoder may be fed to a visual display of alpha-numericform via means for converting the output into units of length, i.e. feet and/or metres and sub-multiples thereof.

The means is preferably a microprocessor having storage facilities and programmed to enable a user to store measured distances and to perform calculations involving the measured distances. The microprocessor may have an output portfortransferring stored data to a computer orto a printer for providing a print-out of the data.

The housing 2 is divided into two parts 2a and 2b, of which the laser source 1 and the beam splitter4 occupy part 2a whilst the remaining components occupy part 26. The division between the two parts is represented by the dotted lines 12.

Part 2a ofthe housing is arranged to be rotatable with respect to part 2b about an axis that lies in the plane containing the beams 5 and 6. Preferably, the axis passes centrally through the beam splitter 4.

A protractor scale (not shown) is mounted upon the part 2a orthe part 2b to enable a userto measure the angular rotation of the part 2a with respect to the part2b.

To measure distances, the laser is energised and the user orientatesthe housing so as to direct beam 5 towards an objectwhose distancefromthe user isto be measured. In Figure 1, the object is represented diagrammatically at 13. Impingement of beam 5 on the surface of the object shows as a visible area of light. Reflector 8 is then rotated to incline beam 6 with respect to beam Sto direct the latter to impinge on the surface of the object and the rotation is adjusted until the area of light resulting from the impingement of beam 6 coincides exactly with the area of lightfrom beam 5.

The distance to the object is then derived from the equation X = Ytan Where Xis the distance to the object, Y is the distance between the centres of the beam splitter4 and the reflector8 and A isthe angle of inclination of beam 6 with respect to beam 5, i.e.

the inclination ofthe reflector 8.

The apparatus may also be used to measure the angle between selected points. Thus, from the position shown in Figure 1, a user rotates the part 2a of the housing 2 until beam 5 impinges on a selected pointwhose angulardisplacementfrom the pointof impingement of beam 5 on object 13 is required. The userthen reads the angle through which the part 2a has been rotated using the protractorscale.

It will be understood that it is possible to produce angular movement of beam Sin ways other than that described above. Forexample,the introduction of refractor between beam splitter 4 and aperture 7 that is so mounted as to produce the angular movement of the beam by suitable movement of the refractor may be used. In this case, the aperture 7 must be large enough to accommodate the movement ofthe beam 5.

In addition, in an alternative embodiment,the beam 5 is fixed and beam 6 is movable both in the plane containing the beams 5 and 6 and in a plane at right angles thereto. This may be achieved by so mounting the reflector8that it is capable of the required movement, or by using a refractor between the reflector8 and the slot 9.

The housing 2 may be a hand-held unit for ex- ample of the form shown at 13 in Figure 2. The unit is of generally rectangularform when seen in end and side elevations and has the slot9 and aperture7 in one end wall. The housing 2 is cut away as at 14to provide a grip by means of which the user is able to grasp the unit.

External of the unit and conveniently located upon a sidewall 15 is a control knob 16 by means ofwhich the user is able to rotate the reflector8.

An upper part 2b ofthe housing is rotatable as indicated by the arrows 17 to rotate beam 5 as described above. A scale 18 on the upper surface ofthe housing enables a user to read off the angularvalue ofthe rotation.

Located within the unit is the microprocessor which is adapted to energise a display 19 preferably a liquid crystal display.

The knob 16 may also operate an ON/OFF switch for the laser source housed within the unit or a sep- arate ON/OFF switch may be provided. The laser source is a ruby laserforexample or it may bea helium-neon laser or other gas laser or it may be a helium-cadmium laser.

Control buttons 20 on the unit allow a userto select the particular units in which a distance is to be measured and to output stored measurements to other equipment as described above. The display distance may take into account the front-to-rear length ofthe unit by operating another of the buttons 20.

The use of coherent light produces very sharply defined areas of light upon the object.

The use of optically visible radiation enables the apparatus to be used under conditions of little or no natural light, for example it is particularly suitable for use in mines where lighting is poor or non-existent.

Obviously, the described apparatus is usable only when the areas of light can be observed sufficiently clearly to enable the accurate registration referred to above to be effected but this is usually so where the distances involved are of the values indicated above.

To improve observation of the areas of light, the apparatus may be fitted with a telescope or a tele scopic sight through which the user is able to observe the registration of the areas of light. Thetele- scope/telescopic sight may be fitted with a graticule.

Forvery short distances, conventional light sources may be used in conjunction with collimating meansto produce narrow, substantiallynon- divergent beams of light.

The unit may be of a configuration that a user can hold against his body to give a greater degree of stability than may be possible with the hand-held de- sign of Figure 2. The configuration may incorporate a carrying strap or straps which the user can place over his head to supportthe container. In such a case, the control knob may be on the front or on the side ofthe container and the display may be on the upper surface thereof in a location in which itis readily visible to the user.

Claims (10)

1. Apparatus for measuring distance and angles comprising means for projecting a beam of light from the apparatus, an arrangement for projecting from the apparatus a second beam of lightthat is spaced from the first beam, an arrangement for in clining one beam relatively to the other, means for measuring the inclination, and further means for imparting angular movement to one of the beams about an axis lying in the plane containing thefirst and second beams and for measuring that movement.

2. Apparatus as claimed in claim 1 in which one only ofthe beams is inclinable and in which onlythe other beam is angularly movable.

3. Apparatus as claimed in claim 1 or 2 comprising a housing a part of which accommodates a light source for providing the other beam, and in which the part is mounted upon the remainder of the hous- ing in such mannerthatthe part is movable to impart angular movement to the beam.

4. Apparatusasclaimed in claim 1 or2and further comprising optical means for imparting angular movement to the said beam.

5. Apparatus as claimed in claim 3 in which the light source provides both beams.

6. Apparatus as claimed in claim 4 in which a single light source provides both beams.

7. Apparatus as claimed in claim 5 or 6 in which the light source is a source of coherent light.

8. Apparatus as claimed in claim 7 in which the light source isa pulsed lasersource.

9. A hand-holdable apparatus for measuring distance and angles comprising apparatus as claimed in any one ofthe preceding claims.

10. Apparatus for measuring distance and angles substantially as herein described with reference to and as illustrated by the accompanying drawings.